The present invention relates to a turbine bucket for a gas turbine stage and particularly relates to a second stage turbine bucket airfoil profile.
In recent years, advanced gas turbines have trended toward increasing firing temperatures in order to meet system requirements of efficiency and loading. Consequently, the design and construction of turbine buckets require optimized aerodynamic efficiency as well as optimized aerodynamic and mechanical bucket loading.
In accordance with a preferred embodiment of the present invention, there is provided a unique turbine bucket airfoil profile for the buckets of a turbine stage, preferably the second stage of a gas turbine. The bucket airfoil profile is defined by a unique loci of points to achieve the necessary efficiency and loading requirements whereby improved turbine performance is obtained. These unique loci of points define the nominal airfoil profile and are identified by the X, Y and Z Cartesian coordinates of Table I which follows. The 3600 points for the coordinate values shown in Table I are for a cold, i.e., room temperature profile at various cross-sections of the bucket airfoil along its length. The X and Y coordinates are given in distance dimensions, e.g., units of inches, and are joined smoothly at each Z location to form a smooth continuous airfoil cross-section. The Z coordinates are given in non-dimensionalized form from 0 to 1 along a bucket centerline coincident with a radius from the axis of rotation. By multiplying the airfoil height dimension, e.g., in inches, by the non-dimensional Z value of Table I and adding that value to the root radius of the bucket, the actual Z distance from the rotational axis, e.g., in inches, is obtained. Each defined cross-section is joined smoothly with adjacent cross-sections to form the complete airfoil shape.
It will be appreciated that as each bucket airfoil heats up in use, the profile will change as a result of stress and temperature. Thus, the cold or room temperature profile is given by the X, Y and Z coordinates for manufacturing purposes. Because a manufactured bucket airfoil profile may be different from the nominal airfoil profile given by the following table, a distance of plus or minus 0.160 inches from the nominal profile in a direction normal to any surface location along the nominal profile and which includes any coating process, defines the profile envelope for this bucket airfoil. The design is robust to this variation without impairment of the mechanical and aerodynamic functions.
It will also be appreciated that the airfoil can be scaled up or scaled down geometrically for introduction into similar turbine designs. Consequently, the X and Y coordinates in inches and the Z coordinates, when converted to inches, of the nominal airfoil profile given below are a function of the same constant or number. That is, the X and Y and optionally the Z coordinate values in inches may be multiplied or divided by the same constant or number to provide a scaled up or scaled down version of the bucket airfoil profile while retaining the airfoil section shape.
In a preferred embodiment according to the present invention, there is provided a turbine bucket having a bucket airfoil shape in an envelope within xc2x10.160 inches in a direction normal to any airfoil surface location wherein the airfoil has a nominal profile substantially in accordance with Cartesian coordinate values of X, Y and Z set forth in Table I wherein Z is a non-dimensional value along a bucket centerline coincident with a radius from a turbine axis of rotation convertible to a Z distance in inches from said turbine axis by multiplying the Z value by a height of the airfoil and adding that product to a root radius of the bucket and wherein X and Y are distances in inches defining the airfoil profile at each distance Z, the profiles at the Z distances being joined smoothly with one another to form a complete airfoil shape.
In a further preferred embodiment according to the present invention, there is provided a turbine bucket having an uncoated nominal airfoil profile substantially in accordance with Cartesian coordinate values of X, Y and Z set forth in Table I wherein Z is a non-dimensional value along a bucket centerline coincident with a radius from a turbine axis of rotation convertible to a Z distance in inches from said turbine axis by multiplying the Z value by a height of the airfoil and adding that product to a root radius of the bucket and wherein X and Y are distances in inches defining the airfoil profile at each distance Z, the profiles at the Z distances being joined smoothly with one another to form a complete airfoil shape, the X and Y distances being scalable as a function of the same constant or number to provide a scaled-up or scaled-down bucket airfoil.
In a further preferred embodiment according to the present invention, there is provided a turbine comprising a turbine wheel having a plurality of buckets, each of said buckets having an airfoil shape in an envelope within xc2x10.160 inches in a direction normal to any airfoil surface location wherein the airfoil has a nominal profile substantially in accordance with Cartesian coordinate values of X, Y and Z set forth in Table I wherein Z is a non-dimensional value along a bucket centerline coincident with a radius from a turbine axis of rotation convertible to a Z distance in inches from said turbine axis by multiplying the Z value by a height of the airfoil and adding that product to a root radius of the bucket and wherein X and Y are distances in inches defining the airfoil profile at each distance Z, the profiles at the Z distances being joined smoothly with one another to form a complete airfoil shape.
In a further preferred embodiment according to the present invention, there is provided a turbine comprising a turbine wheel having a plurality of buckets, each of said buckets having an uncoated, nominal airfoil profile substantially in accordance with Cartesian coordinate values of X, Y and Z set forth in Table I wherein Z is a non-dimensional value along a bucket centerline coincident with a radius from a turbine axis of rotation convertible to a Z distance in inches from said turbine axis of rotation by multiplying the Z value by a height of the airfoil and adding that product to a root radius of the bucket and wherein X and Y are distances in inches defining the airfoil profile at each distance Z, the profiles at the Z distances being joined smoothly with one another to form a complete airfoil shape, the X and Y distances being scalable as a function of the same constant or number to provide a scaled-up or scaled-down bucket airfoil.